The jetliner's digital signature shows the plane was probably descending the last time it was in touch with a satellite, meaning the wreckage could be more than 20 miles to the west or 30 miles to the east from the flight's path over the southern Indian Ocean, Martin Dolan, the commissioner of the Australian Transport Safety Bureau, the agency overseeing southern search efforts for the doomed plane, told ABC News.

Search efforts off Australia's coastline have been fruitless, with air crews and underwater vehicles scouring ocean waters for clues in the plane's disappearance.

Investigators believe the jetliner had been flying for more than seven hours, cruising at altitude with apparently no damage, pinging a satellite every hour.

The final full ping occurred at 8:11 a.m. But eight minutes later, an unexpected ping occurred, reflecting fuel exhaustion.

By that point, the jet was descending, Dolan said. Investigators are still unsure whether the jet was dropping out of the sky or still flying.

The location of the jet could depend on whether both engines quit at the same time. If so, the jet could have glided for a while, he said, leaving considerable range for the plane's final location.